Miners worldwide have been smelting non-ferrous metal ores in various types of smelters for many years. The capital investment in these smelter furnaces is high and the technology behind these smelters is relatively mature. Smelter furnaces are shut down periodically for scheduled maintenance halting throughput of precious metals. While effort has always been made to minimize the number of down days during scheduled maintenance and to extend the intervals between maintenance, due to unprecedented global demand, there is strong incentive to minimize down time and meet production targets.
A common cause that requires repair and shut down of the smelter furnace is damage to the interior sidewall of the furnace. The molten bath in a range of 1200-1600° C. exerts an aggressive thermal load on the sidewall and its corrosive properties cause further erosion and damage to the sidewall. The industry has long been lining the walls of furnaces with refractory and copper coolers for protection as illustrated in FIGS. 1, 1A, 1B, and 1C. The coolers maintain an isotherm of frozen slag preventing further erosion of the refractory thereby preserving the structural integrity of the furnace.
FIG. 1 is a schematic 100 of one example (one arrangement) of cooling conduits which may reside in a copper cooler. FIG. 1 is an example of a heat exchanger wherein coolant conduits are arranged as shown. Reference numeral 102 indicates an inlet conduit leading to a u-shaped joint 104. U-shaped joint 104 interconnects with intermediate conduit 101 which in turn leads to and is interconnected with U-shaped joint 105. Reference numeral 103 indicates an outlet conduit which is interconnected with the intermediate conduit. Generally, as used herein the U-shaped joints/end connections 104, 105 are included within the definition of the intermediate conduit. The intermediate conduit includes all of the horizontal conduits and U-shaped joints.
FIG. 1A is a schematic 100A of a cooling conduit illustrated in phantom inside a copper cooler 106. Coolant is forced through the cooling conduits within the copper cooler absorbing heat from the process. Copper has a high thermal conductivity which conducts heat to the cooling conduits where the heat is transferred to the coolant which is then dumped to a reservoir/heat sink (not shown).
FIG. 1B is a schematic 100B of a copper cooler 106. FIG. 1C is a schematic 100C of another copper cooler illustrating multiple cooling ports 107, 108, 109, 110, 111, 112, 113, and 114 into and out of the cooler. The ports indicate multiple cooling loops/paths through the copper cooler.
As the condition of the molten metal bath changes, the molten bath may erode the refractory and eventually burn through the sidewall. Under these conditions, not only does the furnace need to be shut down for repair, the molten metal at a temperature of 1200-1600° C. could seriously injure crews working around the furnaces and impact the surrounding environment. Furthermore, damage to the expensive copper coolers is likely if contacted with the molten bath, introducing safety concerns due to a possible explosion. Overall, serious safety, environmental, and economic consequences can result from a compromised sidewall. Operators of these furnaces have longed for a non-destructive method for monitoring and determining the condition of the refractory inside the furnaces. Currently, with the exception of thermography and some ultrasound techniques, there are no known technologies which are effective to prevent the aforementioned deficiencies.